There are other reasons why a call may be forbidden, or barred and there is a 'Barred Calls Log' function with the 'Logs' tab.

The 'Barred
Calls Log' expands upon the CDR 'Hangup Cause' by giving a detailed
reason for a call that has been barred and is an excellent first for to
call for troubleshooting. For a list of error codes / reasons please
refer to Barred Calls Error Codes.